1. Field of the Invention
The present invention relates to a method and an apparatus for forming a silicon-containing insulation film having a low dielectric constant.
2. Description of the Related Art
As semiconductors have progressed to accommodate a demand for high speed and high density in recent years, a reduction of capacitance between lines is required to avoid signal delays in the multi-layer wiring technology field. Because a reduction in the dielectric constant of a multi-layer wiring insulation film is required in order to reduce the capacitance between lines, insulation films having low dielectric constants have been developed.
Conventionally, silicon oxide (SiOx) film is formed by adding oxygen (O2) or nitric oxide (N2O) as an oxidizing agent to a silicon source gas such as SiH4 and Si(OC2H5)4 and applying heat or plasma energy to the source gas. A dielectric constant (ε) of this film was approximately 4.0.
By contrast, by using a spin-coat method using inorganic silicon oxide glass (SOG) materials, a low dielectric constant insulation film having a dielectric constant (ε) of approximately 2.3 was formed.
By using a plasma CVD method with CxFyHz as a source gas, a low dielectric constant fluorinated amorphous carbon film having a dielectric constant (ε) of approximately 2.0–2.4 was formed.
Further, by using a plasma CVD method using a silicon-containing hydrocarbon (for example, P-TMOS (phenyltrimethoxysilane) as a source gas, a low dielectric constant insulation film having a dielectric constant (ε) of approximately 3.1 was formed.
Additionally, by using a plasma CVD method using a silicon-containing hydrocarbon having multiple alkoxy groups as a source gas, a low dielectric constant insulation film having a dielectric constant (ε) of approximately 2.5 was formed when optimizing film formation conditions.
However, the above-mentioned conventional approaches have the following problems:
In the case of the inorganic SOG insulation film formed by the spin-coat method, there are problems in that the materials properties are not distributed equally on a silicon substrate and that a device used for a curing process after coating the material is expensive.
In the case of the fluorinated amorphous carbon film by the plasma CVD method using CxFyHz as a source gas, there are problems such as low heat resistance (370° C.), poor adhesion with silicon materials, and low mechanical strength of the film formed.
Furthermore, among silicon-containing hydrocarbons, when P-TMOS is used, a polymerized oligomer cannot form a linear structure such as a siloxane polymer because P-TMOS contains three alkoxy groups. Consequently, a porous structure is not formed on a silicon substrate, and hence a dielectric constant cannot be reduced to a desired degree.
Additionally, when a silicon-containing hydrocarbon containing multiple alkoxy groups is used, a polymerized oligomer can form a linear structure such as a siloxane polymer by optimizing film formation conditions. Consequently, a porous structure can be formed on a silicon substrate and a dielectric constant can be reduced to a desired degree. However, there are problems in that oligomers having the linear structure have weak bonding power therebetween and thus the mechanical strength of a resultant film is low.